Ethernet adaptors are utilized to communicate between network nodes through various transmission mediums. A node in a network utilizes an ethernet adaptor at that node to allow communication with a “switch” via a desired transmission medium. This transmission medium could be a CAT5 cable, an optical fiber cable or a coax cable. The hub is operable to interface with the particular transmission medium in a predetermined manner, and is operable to interconnect any given node with other nodes on the network.
Each ethernet adaptor requires the processing capability necessary to interface with a particular transmission medium in accordance with a predetermined protocol. CAT5 cable and coax utilize what is referred to as “copper” wire connections, whereas optical systems utilize an optical fiber. Both of these different mediums utilize distinctly different communication techniques, which are well known in the art. In order to provide the versatility of a given hub, manufacturers have recently adopted a pluggable package configuration that allows modules to be inserted into various slots to accommodate different transmission mediums. One type of pluggable module is referred to as a Small Form-Factor Pluggable (SFP) module. The SFP has a fairly restrictive specification that defines the input/output configuration for adapting or for mating with a particular slot, the power requirements and data transmission characteristics thereof, etc. Of these, each SFP has a limited power budget and a defined input voltage, of 3.3 volts. Thus, the only voltage available to the SFP is this 3.3 volt level, with a maximum power requirement of approximately 1.0 watts.
This limited power budget presents a problem when adapting multiple ethernet configurations to an SFP. As the upper end frequency of the ethernet adaptor increases, so does the processing power required to accommodate such high bandwidths, such as one gigabit, two gigabit and ten gigabit configurations. This processing is typically provided by a Digital Signal Processor (DSP), which requires a considerable amount of power to operate. Further, due to the density level of the chip and the associated manufacturing process, the voltage level associated with the DSP is typically 1.2 volts, utilizing a 0.13 micron process. This presents a problem to the designer of the SFP in that some type of voltage regulation is required in order to provide a step down in voltage from 3.3 volts to 1.2 volts. This has been heretofore accommodated by utilizing separate voltage regulator chips. Typically, these voltage regulator chips, for efficiency reasons, utilize a synchronous switcher. This synchronous switcher is operable to utilize some type of reactive circuit, such as an inductor and capacitor, and one or more switches to switch current to the reactive element from the supply and from ground. However, these typically require a separate integrated circuit to be fabricated and disposed within the SFP, thus increasing the cost of the part. One reason that such a separate chip is required is that the technology utilized to realize the synchronous switcher involves a manufacturing process different from the manufacturing process associated with the ethernet adaptor. Typically, bipolar technology or BiCMOS technology is utilized in the synchronous switcher, whereas primarily CMOS technology is utilized in the circuitry of the ethernet adaptor circuit. Thus, utilizing conventional synchronous switcher fabrication processors in conjunction with the CMOS technology for the ethernet adaptor circuit teaches against integrating the synchronous switcher onto the same chip with the ethernet adaptor. Further, when analog and digital circuitry are combined on the same integrated circuit in combination with switching transistors associated with the switcher functionality, there exists the possibility for forward biasing of the substrate diode due to the inductive element associated with the switcher pulling the voltage on a node below the substrate voltage. This can introduce unwanted noise into the substrate.